Suspension and braking assembly

ABSTRACT

A suspension and braking assembly for a wheel of vehicle, comprises a suspension link, a hub mounted on the suspension link for rotation relative thereto, a brake disc mounted for rotation with the hub, friction material pads arranged on opposite sides of the disc, and a piston and cylinder assembly operable to urge the pads against the disc. The link comprises top and bottom mounts for supports. The suspension link also comprises the cylinder of said piston and cylinder assembly which is formed integrally with the remainder of the link. Said disc is mounted for limited movement on the hub in a direction generally parallel to the axis about which the hub rotates.

This invention is concerned with a suspension and braking assembly for awheel of a vehicle.

A conventional suspension and braking assembly comprises a suspensionlink, and a hub mounted on the suspension link for rotation relativethereto, the hub providing a mounting for the wheel. In order to enablethe wheel to be braked, the assembly also comprises a disc brakecomprising a brake disc mounted for rotation with the hub, frictionmaterial pads arranged on opposite sides of the disc, and at least onepiston and cylinder assembly operable to urge the pads into engagementwith opposite side surfaces of the disc to brake the hub and hence thewheel. Conventionally, in order to mount the piston and cylinderassembly of the braking system, a slide is bolted to the suspension linkand the piston of said piston and cylinder is slidably mounted on thisslide. The disc is conventionally rigidly fixed to the hub and wear ofthe pads and/or disc is accommodated by the sliding movement of thecylinder.

Conventionally, a suspension link also comprises top and bottommountings for supports of the link. The top mounting may receive a strutof the McPherson type which defines an axis about which the link can bepivoted to turn a wheel mounted on the hub about said axis.Alternatively, the top mounting may receive a top wishbone. The bottommounting may receive a bottom wishbone. Where the wheel is used to steerthe vehicle, the arm also conventionally comprises an arm for connectionto a track rod of a steering system of the vehicle by operation of whichthe link can be turned to steer the vehicle.

U.S. Pat. No. 3,941,221 discloses a suspension and braking assemblywhich is largely fabricated from sheet metal. The assembly comprises apiston and cylinder assembly having its cylinder welded to a suspensionlink. The assembly also comprises a brake disc which can slide on a hubof the assembly. However, this assembly would require excessive time tomanufacture and has nothing to control the movement of its brake disc onits hub so that it is doubtful whether it would operate well.

The conventional suspension and braking assembly described aboveoperates well but is a relatively heavy item. Accordingly, it is anobject of the present invention to provide a suspension and brakingassembly which is easy to manufacture and has a reduced weight.

The invention provides a suspension and braking assembly for a wheel ofa vehicle, the assembly comprising a suspension link which comprises topand bottom mountings for supports of the link, and a hub mounted on thesuspension link for rotation relative thereto, the hub providing amounting said wheel, the assembly also comprising a brake disc mountedfor rotation with the hub, said disc also being mounted for limitedmovement on the hub in a direction generally parallel to the axis aboutwhich the hub rotates, the assembly also comprising friction materialpads arranged on opposite sides of the disc, and a piston and cylinderassembly operable to urge the pads into engagement with opposite sidesurfaces of the disc to brake the hub and hence the wheel, characterisedin that the suspension link also comprises the cylinder of said pistonand cylinder assembly which is formed integrally with the remainder ofthe link, and in that the assembly also comprises resilient forceapplying means acting between the hub and the brake disc to control themovement of the disc on the hub.

In a suspension and braking assembly according to the invention, thecylinder of the piston and cylinder assembly is integral with thesuspension link avoiding the slide and mountings for a cylinder on theslide. It is found that this arrangement enables a significant reductionin weight to be achieved, eg a 25% reduction has been found to bepossible with one design. The assembly's cost is also reduced. Themovement of the disc on the hub accommodates wear of the pads or thedisc. The resilient force applying means acts to prevent the disc fromslewing on the hub, to take up slack caused by greater thermal expansionof the disc than the hub, and to prevent the disc from rattling on thehub.

Preferably, in an assembly according to the invention, the disc hasinwardly-projecting teeth which engage splines on the hub. The splinesmay be spaced, eg by being arranged in groups, and, said resilient forceapplying means may comprise springs mounted on the hub between thesplines. There are suitably three groups of splines and, hence, threesprings which are equally-spaced circumferentially and give athree-point location. The springs are suitably leaf springs secured tothe hub at a location centrally between adjacent groups of splines. Theleaf springs, then, engage the disc at their ends.

Since conventional disc brakes with a single disc require considerablepressure to be applied between the pads and the disc to enable therequired torque to be generated, this high pressure causing wear andbeing expensive to generate, it is desirable to reduce the pressurerequired. In order to achieve this, an assembly according to theinvention may also comprise a second disc mounted on the hub beside saiddisc, the second disc also being mounted for limited movement on the hubin a direction generally parallel to the axis about which the hubrotates and being acted upon by said resilient force applying means, theassembly also comprising brake pads mounted between said discs forlimited movement in said direction. The second disc enables the brakingtorque to be shared among four surfaces instead of the conventional two,thereby reducing pressure, heat generated, and wear. It is known toutilise two discs in the disc brake of a wheel; see, eg U.S. Pat. No.4,598,799 and GB 2 076 087.

Where the wheel is to be used for steering, the link also comprises anarm for connection to a track rod of a steering system of the vehicle.

There now follows a detailed description, to be read with reference tothe accompanying drawings, of a suspension and braking assembly which isillustrative of the invention.

In the drawings:

FIG. 1 is an exploded view of the illustrative assembly;

FIG. 2 is a side elevational view of the illustrative assembly;

FIG. 3 is similar to FIG. 2 but shows the illustrative assembly invertical cross-sectional;

FIG. 4 is a view taken in the direction of the arrow IV in FIG. 2;

FIG. 5 is a view taken in the direction of the arrow V in FIG. 2;

FIG. 6 is a vertical cross-sectional view taken through a suspensionlink of the illustrative assembly; and

FIG. 7 is a view similar to FIG. 4 but of a modification of theillustrative assembly.

The illustrative assembly 10 is a suspension and braking assembly for afront wheel (not shown) of a front wheel-drive car. The assembly 10comprises a suspension link 12 and a hub 14 mounted on the suspensionlink 12 for rotation relative thereto.

The hub 14 is an integral casting and, as is conventional, has a hollowcylindrical rearward projection 14a which has a splined interior and anexterior which provides a mounting for roller bearings 16 (FIG. 3). Asplined projection of a constant velocity joint 18 (shown in broken linein FIG. 3) at the end of a drive shaft is received within the projection14a so that the hub 14 can be rotated on the bearings 16 by the driveshaft. The hub 14 also has an annular disc-like portion 14b from whichthe portion 14a projects rearwardly. The hub 14 provides a mounting forthe wheel (not shown) which is bolted against a forward surface of theportion 14b by bolts received in holes 14d. The hub 14 also has a hollowcylindrical rearward projection 14c of greater diameter than the portion14a. The portion 14c projects from the outer edge of the portion 14b.The portion 14c has an outer surface provided with splines 20 runningparallel to the axis 22 about which the hub 14 rotates. The splines 20are arranged in three equally circumferentially-spaced groups.

The suspension link 12 (see FIG. 6) is an integral casting and comprisesa hollow cylindrical portion 12a of conventional form which provides amounting for the bearings 16 so that the hub 14 rotates on the link 12.The link 12 also comprises top 24 and bottom 26 mountings for supportsof the link 12. The top mounting 24 is provided by a portion 12b of thelink 12 which projects rearwardly from a portion 12c which projectsupwardly from the portion 12a. The portion 12b is of conventional formand forms two semi-cylindrical arms (see FIG. 5) which together form aclamp which can be tightened by a bolt (not shown) which extends throughbores 28 in the arms and across a gap between them. A McPherson strut(not shown) can be clamped between the arms of the portion 12b so thatthe link 12 can pivot about the longitudinal axis of the strut.

The bottom mounting 26 is provided by a portion 12d of the link 12 whichprojects downwardly from the portion 12a thereof. This portion 12d is ofconventional form and has a vertical bore 30, to receive a pin of a balljoint (not shown), and two horizontal bores 32 in which bolts (notshown) can be received to connect the link 12 to a tie bar (not shown).

The link 12 also comprises an arm 34 for connection to a track rod (notshown) of a steering system of the vehicle. This arm 34 is ofconventional form and is provided by a portion 12e of the link 12 whichprojects sideways from the portion 12a thereof. The arm 34 comprises avertical bore 36 through which the arm can be pivotally connected to thetrack rod. In order to steer the vehicle, the track rod is moved tocause the link 12 to pivot on the joint 18 and the mountings 24 and 26.

The illustrative assembly 10 also comprises two brake discs 38 and 40which are mounted for rotation with the hub 14. The two discs 38 and 40are identical to one another and are mounted for limited movement on thehub 14 in a direction generally parallel to the axis 22 about which thehub rotates. Specifically, each disc 38 and 40 is in the form of a flatannular plate and has inwardly-projecting teeth 42. The teeth 42 of eachdisc 38 and 40 are arranged in three groups which match the three groupsof splines 20 on the hub 14. The discs 38 and 40 are fitted over theportion 14c of the hub 14 so that the teeth 42 mesh with and engage thesplines 20 so that rotation of the hub 14 rotates the discs 38 and 40.

Three leaf springs 44 are mounted on the hub 14 to provide resilientforce applying means to apply radial forces between the hub 14 and thediscs 38 and 40. These radial forces prevent the discs 38 and 40 fromtilting on the hub 14, prevent rattling, and control sliding of thediscs along the hub. The resilience of the springs 44 allows thermalexpansion to be accommodated. The springs 44 are secured by screws 46 tothe outer surface of the hub portion 14c in the gaps between the groupsof splines 20. Each spring 44 engages both of the discs 38 and 40 in thegaps between the groups of teeth 42, giving a resilient three-pointmounting for each disc. The discs 38 and 40 can slide on the hubparallel to the axis 22 with the teeth 42 sliding between the splines20.

The illustrative assembly 10 also comprises friction material padsarranged on opposite sides of each of the discs 38 and 40. These padscomprise a first pad 50 which is mounted on a backing plate 52 and isarranged to engage a side surface of the disc 38, pads 54 and 56 whichare mounted on opposite sides of a backing plate 58 and are arranged,respectively, to engage the opposite side surface of the disc 38 and afacing side surface of the disc 40, and a pad 60 which is mounted on abacking plate 62 and is arranged to engage the opposite side surface ofthe disc 40. The backing plate 62 is fixedly mounted on a guide member64 which is in turn fixedly mounted on the portion 12c of the link 12.Specifically, two bolts 66 pass through bores through the portion 12cand the guide member 64, and have threaded ends which are received inthreaded bores in the backing plate 62. The guide member 64 provides twoguidance surfaces 68 on which the backing plates 52 and 58 slide. Theguidance surfaces 68 extend, parallel to the axis 22, along oppositesides of the member 64. Each guidance surface 68 is generally convex andU-shaped in transverse cross-section and is received within concaveU-shaped projections of the backing plates 52 and 58. A leaf spring 70is positioned between the guide member 64 and the backing plates 52 and58 to prevent rattling.

The illustrative assembly 10 also comprises a piston and cylinderassembly operable to urge the pads 50, 54, 56 and 60 into engagementwith opposite side surfaces of the discs 38 and 40 to brake the hub 14and hence the wheel. The piston and cylinder assembly comprises acylinder 72 which is defined by the portion 12c of the link 12. Thus,the cylinder 72 is formed integrally with the remainder of the link 12.The piston 74 of the assembly projects from the cylinder 72 and engagesthe backing plate 52 on the opposite side thereof to the pad 50. Thepiston and cylinder assembly is operated by supplying hydraulic fluidunder pressure to a bore 76 in the link portion 12c which communicateswith the cylinder 72. The piston 74 moves out of the cylinder 72 movingthe backing plates 52 and 58 and the discs 38 and 40 until the disc 40engages the pad 60 which does not move.

FIG. 7 is similar to FIG. 4 but illustrates a variation 100 of theillustrative assembly 10 in which like parts to those of the assembly 10are given the same reference numerals and are not further described. Theassembly 100 differs from the assembly 10 in that, instead of thecylinder 72, the portion 12c of the link 12 has two parallel cylinders102 formed therein. In this case, each of the cylinders 102 has asmaller transverse cross-sectional area than the cylinder 72 but thetotal area of the cylinders 102 is greater. Each of the cylinders 102has a piston 104 therein and the pistons 104 cooperate in pressing thebacking plate 52. In order to accommodate the two piston and cylinderassemblies, the guide member 64 is modified to arch over the pistons 104as shown at 106 and the bolts 66 are replaced by three bolts 108. Theuse of two piston and cylinder assemblies enables greater force to beapplied for the same pressure in the cylinders (or the same force to beapplied for lower pressure) and this force can, on average, be appliedat a greater distance from the axis 22. If desired, the two cylinderscan be of different diameters, eg with the leading cylinder, in thenormal direction of rotation, being of greater diameter.

What is claimed is:
 1. A suspension and braking assembly for a wheel ofa vehicle, the assembly comprising a suspension link which comprises topand bottom mountings for supports of the link, and a hub mounted on thesuspension link for rotation relative thereto, the hub providing amounting for said wheel, the assembly also comprising a brake discmounted for rotation with the hub, said disc also being mounted forlimited movement on the hub in a direction generally parallel to theaxis about which the hub rotates, the assembly also comprising frictionmaterial pads arranged on opposite sides of the disc, and a piston andcylinder assembly operable to urge the pads into engagement withopposite side surfaces of the disc to brake the hub and hence the wheel,wherein the suspension link also comprises the cylinder of said pistonand cylinder assembly which is formed integrally with the remainder ofthe link, and wherein the assembly also comprises resilient forceapplying means acting between the hub and the brake disc to control themovement of the disc on the hub.
 2. An assembly according to claim 1,wherein the disc has inwardly-projecting teeth which engage splines onthe hub.
 3. An assembly according to claim 1, wherein the splines arespaced and said resilient force applying means comprises springs mountedon the hub between the splines.
 4. An assembly according to claim 1,wherein the assembly also comprises a second disc mounted on the hubbeside said disc, the second disc also being mounted for limitedmovement on the hub in a direction generally parallel to the axis aboutwhich the hub rotates and being acted upon by said resilient forceapplying means, the assembly also comprising brake pads mounted betweensaid discs for limited movement in said direction.
 5. An assemblyaccording to claim 1, wherein the link also comprises an arm forconnection to a track rod of a steering system of the vehicle.